What is the current level of JSA?

What is estimated fault level current of a switch board and how can we calculate it?

• In ships of 440v, 60 Hz, 3No 1500KVA generators --- jst give me outline wht is fault level current, wht happens at this current, how to calculate, fault level current is current at busbar or circuit breaker or something else. Wht is fault clearing capacity of circuit breaker. what is the diff between fault level current and fault clearing capacity.Plz explain

• Answer:

  Just a general statement: 1500k volt-amps so 1500k/440 volts = 3409 amps supplied You could put in a 3400 amp main circuit breaker or lower. Fault level current would be your 3400 amps, normal trip condition. If I remember correctly fault clearing capacity is when the supply goes directly to ground or another phase. Its instant. You can seriously damage the conductors causing them to melt or damage the bus bars. If your breaker doesn't trip fast enough to protect the equipment you have to lower the trip level of the main breaker until its safe. It has to be set within the fault clearing capacity or you can buy inline surge arrestors. I'm not an installer just maintenance.